It's always a shock for me to see some of Glenn Ford's darker performances. I mean, my image of Ford is as Jonathan Kent, Clark Kent's dad in the 1978 Superman, and there are a lot of other movies that reinforce that image of the wholesome American dad. I don't know anything about Ford's biography, so I don't know how true it was to the man, but it doesn't matter, I guess. When I see Ford in something like 3:10 to Yuma or Gilda (surely one of the most homoerotic films of Hollywood's golden age), I get a case of cognitive dissonance. This is NOT the Glenn Ford I'm comfortable with, but he's certainly a lot more interesting. The film that really plays up this duality is Fritz Lang's brutal noir, The Big Heat, from 1953.
You get both sides of the coin in The Big Heat: the devoted father and family man, and the cold, relentless cop out for vengeance. The movie even codes it with its leading ladies. The light side is Jocelyn Brando's devoted, doomed wifey, while the dark is Gloria Grahame's gangster's moll (who, herself, has an interesting level of duality, one made physically manifest in the course of the movie). There's so much emphasis on dichotomies that it almost obscures the fact that the movie isn't so cut and dry. The Big Heat is good at hiding its hand.